This invention relates to hydrant valves or shut-off valves commonly used in aircraft fueling. More particularly, this invention relates to a pilot valve actuator for opening or closing a hydrant valve.
A hydrant valve used in aircraft fueling delivers fuel by connecting fuel storage through an underground pipeline at its inlet to an aircraft through a fueling vehicle equipped with a hydrant valve coupler and hose system at its outlet. For safety reasons, to avoid a collision with an aircraft or a supporting vehicle around the aircraft, hydrant valves are, as a rule, installed in a hydrant pit below ground level. A hydrant valve is designed to be opened or closed by the fueling operator from a distance. This requirement is causal so that if a fuel spill occurs in the vicinity of the hydrant pit, the fueling operator has the ability to terminate the flow of fuel by closing the hydrant valve from a safe distance.
Since electric power is normally lacking in the hydrant pit due to the concern over ignition of the fuel, the hydrant valve cannot be controlled electromechanically. The most commonly accepted method for controlling the opening and closing of hydrant valves is the utilization of pressure, either pneumatic or hydraulic, such that the fueling operator can apply or vent pressure to the hydrant valve through a handle valve and command hose which is commonly called a “deadman”. Due to the high pressure and flow rates sustained by hydrant valves, practically all hydrant valves are pilot operated; that is, the main hydrant valve will be opened or closed by actuating a smaller pilot valve installed in the main hydrant valve.
In prior art hydrant valves, a pilot valve actuator is permanently installed directly on the body of the main hydrant valve. Pneumatic or hydraulic pressure is applied to the actuator through a quick disconnect pressure fitting.
FIG. 1 depicts a prior art hydrant valve 10. The hydrant valve includes a hydrant body 12 which encloses a primary hydrant chamber 14. This hydrant chamber 14 is connected to an inlet 16 and an outlet 18. The hydrant body 12 is secured to a fixed rigid surface by means of connectors 13. A fuel supply (not shown) is introduced to the hydrant chamber 14 through the inlet 16. A fueling vehicle (not shown) receives fuel from the hydrant valve 10 through the outlet 18.
A piston 20 is located within the hydrant chamber 14 and movable between opened and closed positions relative to the inlet 16. When the piston 20 is in the closed position, it prevents the flow of fuel through the inlet 16. A chamber 22 is located within the piston 20. The piston chamber 22 is in communication with the inlet 16 through a passageway 24. The piston chamber 22 is isolated from the hydrant chamber 14 by seals 26 and 28 and a pilot valve 30 as will be described below. Because the piston chamber 22 is in communication with the inlet 16, the pressure within the chamber 22 is equalized with the pressure in the inlet 16. In addition, because the chamber 22 is isolated from the hydrant chamber 14 as described, the pressure in the hydrant chamber 14 is negligible. The piston 20 remains in the closed position because of the equalized pressure exerted in the piston chamber 22 and the opposing pressure exerted in the inlet 16 (see arrows in FIG. 1).
The hydrant valve 10 also includes a pilot valve 30 and an actuator 40. The pilot valve 30 and actuator 40 are essentially permanently attached to the hydrant valve 10 in that they cannot be removed without disassembly of the system. As shown in FIG. 2, the prior art pilot valve 30 blocks communication between the hydrant chamber 14, the piston chamber 22, and the passageway 24. The pilot valve 30 comprises a pilot valve stem 32, a pilot valve seat 34 and a pilot valve return spring 36. The pilot valve return spring 36 biases the pilot valve stem 32 in a closed position against the pilot valve seat 34. The pilot valve 30 also includes pilot openings 38 adjacent the pilot valve seat 34. When the pilot valve stem 32 is against the pilot valve seat 34, flow through the pilot openings 38 is obstructed. The prior art actuator 40 comprises a pressure supply adaptor 42, an actuator plunger 44, an actuator plunger stem 46, and an actuator plunger return spring 48. The pressure supply adaptor 42 includes a quick disconnect connector 43 to connect a source of pressure medium (not shown), i.e., pneumatic or hydraulic fluid. The actuator 40 is sealed to prevent the transfer of pressure medium from the actuator 40 to the pilot valve 30.
In the absence of a pressure supply, the actuator plunger return spring 48 biases the actuator plunger 44 in a closed position. When the actuator plunger 44 is in the closed position the actuator plunger stem 46 extends into the pilot valve 30. The actuator plunger stem 46 is connected to the pilot valve stem 32. The combination of the biasing forces from the actuator plunger return spring 48 and the pilot valve return spring 36 bias the pilot valve stem 32 in a closed position against the pilot valve seat 34.
When a pressure medium is introduced through the pressure supply adaptor 42, the actuator plunger 44 is moved into an open position against the biasing force of the actuator plunger return spring 48. When the actuator plunger 44 moves into the open position, the actuator plunger stem 46 is withdrawn from the pilot valve 30. As the actuator plunger stem 46 is withdrawn from the pilot valve 30, the pilot valve stem 32 is moved from the closed position to the open position against the biasing force of the pilot valve return spring 36. As the pilot valve stem 32 moves away from the pilot valve seat 34, the pilot openings 38 are uncovered. The pilot openings 38 permit communication between the hydrant chamber 14, the piston chamber 22 and the passageway 24. When the hydrant chamber 14, piston chamber 22 and passageway 24 are connected the once equal pressure in the piston chamber 22 and the inlet 16 are made unequal permitting the pressure of the fuel supply in inlet 16 to move the piston 20 into an open position. In this way, fuel is permitted to move from the inlet 16 through the hydrant chamber 14 to the outlet 18.
This prior art hydrant valve presents a number of disadvantages. First, as previously mentioned, hydrant valves are normally installed in an open hydrant pit below ground level. This open exposure to the environment introduces various contaminants into the pit, such as water, spilled fuel, debris, abrasives, etc. While the main hydrant valve itself is relatively well-sealed against such contaminants, the pilot valve and its actuator are easily damaged by the contaminants due to their mechanical nature and the need to be open to the atmosphere.
Second, there are various means of applying the pressure necessary to activate a pilot valve actuator. The pressure could be supplied pneumatically using pressurized air from a compressor on the fueling vehicle. The pressure could also be supplied hydraulically utilizing pressurized fluid stored on the fueling vehicle. In some airports, some vehicles may use pneumatic pressure and other vehicles may use hydraulic pressure. In the prior art hydrant valves described above where the actuator is permanently affixed, various pressure media, i.e., air, fuel, oil, that remains in an actuator may be ingested into fueling vehicles causing cross-system contamination. Such contamination may cause equipment failure in the fueling vehicles.
Third, is a financial concern. It is inefficient for every hydrant valve in an airport to be equipped with a relatively expensive actuator. In the traditional setup, each hydrant valve at an airport carries a pilot valve and actuator. The work involved in maintaining and repairing the actuators on each hydrant valve at a single airport could pose a huge logistical problem. A single airport can have hundreds of hydrant valves. While many airports typically have hundreds of hydrant valves they have only a few tens of fueling vehicles to support them. It would be substantially less expensive to remove the actuator from the hydrant valve and install it on the fueling vehicles such that only a few tens of actuators would be required to control the hundreds of hydrant valves at an airport. This would reduce the initial investment required as the number of actuators are reduced and would also reduce the maintenance costs.
Accordingly, there is a need for a hydrant valve wherein the actuator is not exposed to contaminants by its constant presence in the open hydrant pit. Additionally, there is a need for a hydrant valve where an actuator will not be activated by different pressurized media thereby avoiding cross-system contamination. Further, there is a need for a hydrant valve that is economical in that only enough actuators are present to account for each fueling vehicle connectable to the hydrant valves. The present invention fulfills these needs and provides other related advantages.